You don't actually fight attack the elemental, leave that to the NPC's. The elemental will switch to different elements and you are supposed to talk to the Main NPC to switch to the ward that the elemental is currently in. For example it will say the the elemental switch to the earth element, talk to the NPC and tell him to switch to the earth ward. I apologize but I cannot remember the NPC's name, but he is the guy that starts the quest. Hope this helps, it is how I did it and I did attack the elemental a single time myself...